U.S. patent number 4,684,382 [Application Number 06/834,536] was granted by the patent office on 1987-08-04 for evaporative fuel control canister containing epdm foam filter.
This patent grant is currently assigned to General Motors Corporation. Invention is credited to Ismat A. Abu-Isa.
United States Patent |
4,684,382 |
Abu-Isa |
August 4, 1987 |
Evaporative fuel control canister containing EPDM foam filter
Abstract
An evaporative fuel control canister device containing a
quantity of fuel-absorbing material which includes EPDM elastomeric
foam for improved absorption of both fuel vapor and liquid
fuel.
Inventors: |
Abu-Isa; Ismat A. (Rochester,
MI) |
Assignee: |
General Motors Corporation
(Detroit, MI)
|
Family
ID: |
25267151 |
Appl.
No.: |
06/834,536 |
Filed: |
February 28, 1986 |
Current U.S.
Class: |
96/134; 123/519;
502/402; 55/522; 55/DIG.42 |
Current CPC
Class: |
F02M
25/0854 (20130101); Y10S 55/42 (20130101); F02M
2025/0863 (20130101) |
Current International
Class: |
F02M
25/08 (20060101); B01D 050/00 () |
Field of
Search: |
;55/316,387,522,DIG.42
;123/519-521 ;210/496,924,925 ;502/402 ;521/150 |
References Cited
[Referenced By]
U.S. Patent Documents
|
|
|
3683597 |
August 1972 |
Beveridge et al. |
4181780 |
January 1980 |
Brenner et al. |
4430099 |
February 1984 |
Yanagisawa et al. |
|
Primary Examiner: Nozick; Bernard
Attorney, Agent or Firm: Tung; Randy W.
Claims
The embodiments of the invention in which an exclusive property or
privilege is claimed are defined as follows:
1. In a carbon canister of the type used in a vehicle equipped with
a fuel reservoir and an internal combustion engine with an
induction passage for the purpose of evaporative fuel vapor
control, said canister having a housing, a quantity of fuel vapor
adsorbing material in said housing, a fuel vapor inlet and outlet
means, and an air inlet means, wherein the improvement comprises a
filter means of EPDM elastomeric foam positioned in said housing
for the adsorption of fuel vapor and condensed liquid fuel from
said fuel reservoir and the desorption of the same when fresh
atmospheric air is purged through said filter means into the
induction passage of said internal combustion engine.
2. A canister for use in a system for controlling loss of fuel
vapor from a vehicle having a fuel reservoir and an internal
combustion engine with an induction passage, said canister
comprising
a housing having a cylindrical adsorption chamber defined by a
cylindrical side wall and a first and a second oppositely disposed
end wall,
a quantity of fuel vapor adsorbing material filling said
chamber,
filter means made of EPDM elastomeric foam adjacent to said
adsorbing material,
fuel vapor inlet means in said first end wall adapted for
connection to said reservoir whereby fuel vapor emitted from said
reservoir may be dispersed into said adsorbing material and said
foam filter means,
air inlet means in said second end wall in fluid communication with
said fuel adsorbing material and said foam filter means,
fuel vapor outlet means adapted for connection to said induction
passage whereby said foam filter means adsorbs fuel vapor and
liquid fuel from said fuel reservoir and fuel vapor may be purged
from said adsorbing material and said foam filter means into said
induction passage by the fresh air intake through said air inlet
means.
3. A canister for use in a system for controlling loss of fuel
vapor from a vehicle having a fuel reservoir and an internal
combustion engine with an induction passage, said canister
comprising
a housing having a cylindrical adsorption chamber defined by a
cylindrical side wall and a first and a second oppositely disposed
end wall, said first end wall containing fuel vapor inlet means and
fuel vapor outlet means, said second end wall containing an air
inlet means,
a quantity of fuel vapor adsorbing material filling said
chamber,
filter means made of fuel adsorbing EPDM elastomeric foam having a
density of less than 0.50 gm/cm.sup.3 adjacent to said adsorbing
material and said air inlet means,
fuel vapor inlet means in said first end wall adapted for
connection to said reservoir whereby fuel vapor emitted from said
reservoir may be dispersed into said adsorbing material and said
foam filter means,
air inlet means in said second end wall in fluid communication with
said adsorbing material and said foam filter means,
fuel vapor outlet means adapted for connection to said induction
passage whereby said foam filter means assists in the adsorption of
fuel vapor and liquid fuel and such fuel vapor and liquid fuel may
be purged from said foam filter means to said induction passage by
the fresh air intake through said air inlet means.
Description
FIELD OF THE INVENTION
This invention generally relates to an evaporative fuel control
canister device containing a quantity of fuel-absorbing material
and, more particularly, is concerned with an evaporative fuel
control canister device wherein the fuel-absorbing materials
comprise EPDM elastomeric foam.
BACKGROUND OF THE INVENTION
In a vehicle equipped with an internal combustion engine,
evaporative fuel control canister type devices are used for
controlling loss of fuel vapor from fuel tanks and fuel-dispensing
units such as carburetors. A common canister device containing a
quantity of fuel-absorbing materials such as activated charcoal is
connected to the fuel tank vents and the fuel-dispensing unit vents
which stores the fuel vapor emitted therefrom. During vehicle
operation, the fuel vapor stored is purged from the fuel-absorbing
material back into the engine induction system.
Activated charcoal has been found a suitable fuel vapor absorbing
material to be used in such a canister device because of its very
large surface area to weight ratio, i.e., the particles of
activated charcoal are extremely porous and have a sponge-like
structure. This open porous structure while extremely effective in
the absorption of fuel vapor can be blocked and loses its
efficiency when coated with liquid fuel. This occurs when liquid
fuel is accidentally spilled into the fuel vapor inlet of a
canister device. The term liquid fuel is used to include liquid
gasoline and other high molecular weight hydrocarbons with six or
more carbon atoms such as benzene, toluene, heptane, and
xylene.
It is therefore an object of the present invention to provide an
evaporative fuel vapor control canister device containing a
quantity of fuel vapor absorbing material having improved fuel
vapor absorbing capability.
It is another object of the present invention to provide an
evaporative fuel vapor control canister device containing fuel
absorbing materials having not only excellent fuel vapor absorption
capability but also excellent liquid fuel absorption
capability.
SUMMARY OF THE INVENTION
In accordance with a preferred embodiment of the present invention,
an evaporative fuel vapor control canister device can be built
which has not only excellent fuel vapor absorption capability but
also superior liquid fuel absorption capability. This is achieved
by the incorporation of an elastomeric foam filter having unique
liquid fuel absorption capability in such a canister device.
We have discovered a unique elastomeric foam material of EPDM
(ethylene-propylene-diene-monomer) which has superior absorption
property for liquid gasoline and other high molecular weight
hydrocarbons. This elastomeric foam material can absorb up to 5
times its own weight of such liquids. When compared with activated
charcoal material, this EPDM elastomeric foam absorbs 3 times more
liquid gasoline and other high molecular weight hydrocarbons than
activated charcoal.
My novel canister device can be used in a system for controlling
loss of fuel vapor and liquid fuel from a vehicle equipped with a
fuel reservoir and an internal combustion engine having an
induction passage. This canister device has a housing which is a
cylindrical absorption chamber defined by a cylindrical sidewall
and two oppositely positioned end walls. The first end wall
contains a fuel vapor inlet and a fuel vapor outlet. The second end
wall contains an air inlet to allow the purging through the
canister device of fresh atmospheric air. A quantity of suitable
fuel-absorbing material such as activated charcoal is used to fill
the cylindrical chamber. One or a number of filters made of EPDM
elastomeric foam are placed in the absorption chamber adjacent to
the fuel-absorbing material and/or the air inlet. To achieve a
maximum absorption efficiency, the density of the EPDM elastomeric
foam filters is kept under 0.5 gm/cm.sup.3.
Fuel vapor escaped from the fuel reservoir and other
fuel-dispensing units enters the carbon canister through the fuel
vapor inlet located in one of the end walls. The vapor is absorbed
by the fuel-absorbing material contained in the canister such as
activated charcoal and EPDM elastomeric foam filters. Accidental
spills of liquid gasoline and other high molecular weight
hydrocarbons into the fuel vapor inlet are absorbed by EPDM
elastomeric foam filters placed between the fuel vapor inlet and
the activated charcoal to prevent potential contamination of the
latter. During vehicle operation, a negative pressure is generated
in the canister to draw fresh atmospheric air from the air inlet
such that fuel vapor absorbed in the activated charcoal and in the
elastomeric foam filter are purged back to the engine induction
passage through the fuel vapor outlet.
BRIEF DESCRIPTION OF THE DRAWINGS
Other objects, features and advantages of the present invention
will become apparent upon consideration of the specification and
the appended drawings, in which:
FIG. 1 is an enlarged sectional view of an evaporative fuel vapor
control canister in elevation showing the construction of the
canister assembly.
FIG. 2 is a graph showing the desorption of liquid fuel from EPDM
elastomeric foam and from activated charcoal.
FIG. 3 is a graph showing the absorption of fuel vapor by activated
charcoal and by EPDM elastomeric foam.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT
Referring initially to FIG. 1 where a sectional view of canister 10
is shown. Canister 10 contains a cylindrical sidewall portion 12
and two oppositely positioned end walls 14 and 16. End wall 16
which is located at the bottom of canister 10 has a hollow center
and a built-in cross bar support 18. The cylindrical sidewall
portion 12 and the end walls 14 and 16 are injection molded of a
high strength and high temperature thermoplastic material such as
nylon 66. They are assembled together by using a vibration welding
technique. In the end wall piece 14, a fuel inlet port 20 and a
fuel vapor outlet port 22 are molded in. A plurality of cavities 24
are also molded in the inner surface of end wall 14 to improve the
absorption efficiency of elastomeric foam filter 26 positioned
between the fuel inlet and the absorption chamber 28.
The composition of my EPDM elastomer foam is shown in Table 1. I
used an EPDM elastomer having a Mooney viscosity number of 45.+-.5
at 260.degree. F. which is commercially available from Exxon under
the tradename of Vistalon.RTM. 6505. According to the manufacturer,
this EPDM elastomer contains 9 wt % ethylene norbornene as the
diene component, 53 wt % of ethylene, and 38 wt % of propylene.
TABLE 1 ______________________________________ Composition of EPDM
Elastomeric Foam Concentration Ingredients Phr by Weight
______________________________________ EPDM rubber 100 Sulfonic
Acid and 5 Paraffinic Oil Blend Paraffinic Oil 15 Stearic Acid 5
Zinc Oxide 5 Sodium Bicarbonate 15 Sulfur .5 Tetramethylthiuram .5
Disulfide 2-Mercaptobenzothiazole .5
______________________________________
The EPDM rubber and other ingredients are mixed in a two-roll mill
cooled by circulating tap water. After mixing, the compound is
molded between two aluminum foils using a 152.times.152 mm steel
mold with a 1.9 mm spacer. I have found that for each 1.9 mm rubber
slab molded, approximately 45 gms of compound is needed. The
compression molding is performed at 60.degree. C. for 5 minutes
under 1000 psi pressure.
After rubber slabs are molded, they are placed in an
air-circulating oven at 180.degree. C. for 10 minutes. The rubber
slabs are foamed and cured during this period of time. I have
estimated that the crosslinking density achieved in the elastomeric
foam is 40.times.10.sup.-6 mole/cm.sup.3 which corresponds to a
molecular weight between crosslinks of 22,000. I have also found
that in order to achieve maximum absorption efficiency, the bulk
density of the EPDM foam should be kept under 0.5 gm/cm.sup.3
preferably in the range of 0.2 to 0.4 gm/cm.sup.3. The cell sizes
were determined to be 0.375 mm to 1.25 mm diameter with the average
cell size being 0.8 mm diameter.
At the bottom of canister 10, EPDM elastomeric foam filters 36 and
38 are supported by a support grid 40 and a bottom end wall 16.
Filters 36 and 38 function not only as fuel absorbent to absorb
fuel vapor and liquid fuel but also as dust filters to allow clean
atmospheric air to purge through the canister. This fresh
atmospheric air carries fuel vapor desorbed from foam filters 26,
36 and 38 and activated charcoal 30 through the fuel vapor outlet
22 into the engine induction chamber (not shown) during vehicle
operations when a negative pressure is generated in the
canister.
It is to be noted that even though three EPDM elastomeric foam
filters are shown in our preferred embodiment, any combination of
EPDM foam filters may be used in an evaporative fuel vapor control
device to assist in the absorption of fuel vapor and to absorb
liquid fuel. I have found that EPDM elastomeric foam filter is
capable of absorbing up to 5 times its own weight of liquid fuel.
This unique absorption capability of liquid fuel prevents the
coating of activated charcoal by liquid gasoline and other high
molecular weight hydrocarbons when the same is accidentally
overflowed or spilled into the canister.
FIG. 2 is a graph showing desorption curves of liquid gasoline from
EPDM elastomeric foam and from activated charcoal. It is seen that
when saturated with liquid gasoline, EPDM elastomeric foam absorbs
nearly three times more liquid gasoline than activated charcoal.
During engine operations where fresh purging air is drawn into the
canister, liquid gasoline and other high molecular weight
hydrocarbons are desorbed from the EPDM foam rubber material into
vapor and purged back into the engine induction passage. FIG. 2
shows that in 60 minutes, more than half of the liquid gasoline
originally absorbed in the EPDM elastomeric foam has been desorbed.
Consequently, an EPDM elastomeric foam filter may be used in
endless cycles of liquid fuel absorption and desorption. It is an
ideal fuel absorbent for evaporative fuel vapor control devices
used in a vehicle.
FIG. 3 is a graph showing absorption curves of gasoline vapor for
activated charcoal and for EPDM elastomeric foam. It is seen that
while EPDM elastomeric foam is not as effective as activated
charcoal in absorbing gasoline vapor, it contributes significantly
to the total absorption of gasoline vapor when used in an
evaporative fuel vapor control device. Therefore, activated
charcoal and EPDM elastomeric foam filters can be used in
combination in an evaporative fuel vapor control device to achieve
maximum absorption of both gasoline vapors, liquid gasoline and
other high molecular weight hydrocarbons.
While my invention has been described in terms of a preferred
embodiment thereof, it is to be appreciated that those skilled in
the art will readily apply these teachings to other possible
variations of my invention.
* * * * *